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Computational Astrophysics

Distribution of the physical quantities along the jet propagation axis. We perform special relativistic MHD simulations in a cylindrical 1.5-dimensional pproximation. Our model reproduces a paired super/subluminal knot motions, taken by the HST observations (Biretta et al. 1999), as a quad RMHD shock system. By assuming a viewing angle of 14$^{\circ$ (Wang \& Zhou 2009), observed apparent speeds 6 $c$ and 0.84 $c$ correspond to $\sim$ 0.99 $c$ and 0.80 $c$, respectively. In our model, these knots are identified as the forward/reverse fast mode MHD shocks (FF/RF in the figure). By the nature of a slow mode MHD shock, it may not be appropriated to mediate a diffusive shock acceleration of high energy particles.

Besides, three fundamentals derived from the simulations (shock compression ratio, degree of magnetization, and magnetic obliquity [magnetic pitch angle] at the fast- mode MHD shocks) are suitable to mediate a Fermi-I process so that we propose that forward/reverse fast-mode MHD shocks are a promising explanation for the observed features, not only with regard to their intrinsic motions, but also the efficiency of high energy particle accelerations. Therefore, we suggest our model may be applicable to many super/subluminal features of AGN jets in general(Nakamura, M. & Meier, 2014, ApJ, 785, 152:http://adsabs.harvard.edu/abs/2014ApJ...785..152N)